Ferrite materials containing titanium or manganese



Dec. 9, 1969 v.- SARA ETAL 3,483,126

FERRITE MATERIALS C NTAINING TITANIUM OR MANGANESE Original Filed May 17. 1966 TiO 2' V 2 L1 0 T10 ZLI O-S'I'IO ZL J O-TI'IO SOLID SOLUTION BINARY PHASE LINES TEMP. RANGE! I050 'C TO I250'C INVENTORS RAYMOND V. SARA MASON C COX NORMAN R.THI LKE 87% A T TORNEV United States Patent 3,483,126 FERRITE MATERIALS CONTAINING TITANIUM 0R MANGANESE Raymond V. Sara, North Olmsted, Ohio, Mason C. Cox, Southbridge, Mass, and Norman R. Thielke, North Olmsted, Ohio, assignors to Union Carbide Corporation, a corporation of New York Continuation of application Ser. No. 577,557, May 17,

1966. This application May 15, 1968, Ser. No. 752,405 The portion of the term of the patent subsequent to July 2, 1980, has been disclaimed Int. Cl. Hillf 1/10; C04b 35/26 U.S. Cl. 25262.59 9 Claims ABSTRACT OF THE DISCLOSURE A ferrite material of spinel structure suitable for use as low loss cores in electric components, the material having the formula:

[771 (Li O-bRO -cFe O ioo-m a'o-rezoo] wherein b is from 0.5 to 2.5; c is from 0 to 4; the sum of b and c is from 2.5 to 4.5; m is from about 20* to about 99 mole percent; R is titanium or manganese; and (R'O-Fe O is a normal ferrite, an inverse ferrite, or a mixed normal and inverse ferrite, the material containing at least about mole percent Fe O and having a magnetic permeability higher than that of the end member (Li O-bRO -cFe O alone.

This application is a continuation of application Ser. No. 577,557, filed May 17, 1966, now abandoned, which is in turn a continuation-in-part of application Ser. No. 273,163, filed Apr. 15, 1963, and now abandoned, and Ser. No. 704,732, filed Dec. 23, 1957, now U.S. 3,096,288.

This invention relates generally to ferrite materials and, more particularly, to a new series of ferritic compositions having improved magnetic properties.

The single figure is a ternary phase diagram which illustrates certain aspects of this inveniton.

Ferrites have rapidly attained commercial importance because of their property of becoming magnetized in the presence of a low-to-medium strength magnetic field. Since this magnetization is not permanent, most of these materials are designated as magnetically soft. Pure iron shows analogous behaviour among the metallic magnetic materials. Ferrites have also been found to have high electrical resistivity, many orders of magnitude above that of metals. Because of this high resistivity, the eddy current losses developed in a ferrite core of a radio frequency transformer, for example, are markedly lower than similar losses in a laminated or powdered iron core.

Most of the ferrite materials proposed in the prior art can be described by the formula RO-Fe O where R is a doubly charged ion or is fractionally composed of two or more ions. Examples of such materials are zinc ferrite, a binary nickel-zinc ferrite, a ternary nickel-copperzinc ferrite, and a quaternary magnesium-manganesenickel-zinc ferrite. Minor additions of other oxides (e.g., Li O; BeO, CaO, and PhD; Ga O Cd O SiO TiO or ZrO have also been proposed for various purposes. In general, however, nearly all the ferrite materials heretofore proposed involve only oxides of divalent metals, either in the original formulation or in the final aggregate resulting from heat treatment.

In contrast to the RO-Fe O compositions of the prior art, the present invention is concerned with compositions in which oxides of other than divalent metals are employed. In accordance with the invention, there is provided a ferrite material of spinel structure suitable for use as low loss cores in electric components, the material having the formula:

wherein b is from 0.5 to 2.5; c is from 0 to 4; the sum of b and c is from 2.5 to 4.5; m is from about 20 to about 99 mole percent; R is titanium or manganese; and (R'O-Fe O is a normal ferrite, an inverse ferrite, or a mixed normal and inverse ferrite, the material containing at least about 10 mole percent Fe O and having a magnetic permeability higher than that of the end member (Li O-bRO -cFe O alone. A preferred group of ferrites of this invention are those of the above formula wherein b is from 0.5 to 2.0 and c is from 1.0 to 4.0.

The end member having the formula referred to hereinafter as the substituted ferrite end member, is described and claimed in the aforementioned US. 3,096,288. The invention of these substituted ferrites was based on the realization that one of the oxides present in the conventional ferrite formula (RO-Fe O' can be replaced by two or more oxides of non-divalent metals. Thus, the composition of the substituted ferrite end members may be designated as one of multiple substitution of oxides other than the RO type for those of the RO type in the usual RO-Fe O- formulation. Although the permutations of multiple oxide substitution as described above are very numerous, the present invention relates mainly to two such systems; the Li O-TiO -Fe O system and the Li O-MnO Fe O system.

Referring now to the ternary phase diagram shown in the drawing, while a great variety of substituted ferrites in the Li O-TiO -Fe O system are useful end members in the present invention, the following compositons are considered especially useful:

(1) Ferrospinel-type compositions along join (2) Two-phase bodies in the compositional areas defined by the compatibility triangles immediately adjacent to the spinel-type solid solution join,

5FE203-Li20 F6203 (a) triangle Li O 5 Fe O -Li O TiO Fe O -Li O TiO (b) triangle Li O-5Fe O -Li O-2TiO -Fe O -Fe O and (c) triangle Li O 2TiO Fe O -Li O TiO -2Li O- 5 TiO (3) Multiphase bodies in the compositional areas defined by the compatibility triangles next most adjacent to the ferrospinel solid solution join:

(a) triangle Li O- Fe O -Li O TiO -Li O -Fe O and (b) triangle Fe O -Fe O -Fe O Tiog.

The normal, inverse, or mixed normal and inverse ferrite end member has the formula (RO-Fe O wherein R is at least one cation selected from the group consisting of zinc, cadmium, copper, magnesium, manganese, nickel, and cobalt. The crystal structure of these ferrites conforms to the cubic structure called the spinel structure, as in the natural mineral MgO-Al O The unit cell of the spinel structure is a cubic arrangement of 32 anions (oxygen ions) with 24 cations (A, B) distributed in certain interstices between the anions. In certain spinels, the type A cations occupy lattice sides formed by four adjoining anions and are said to be tetrahedrally coordinated, while the type B cations occupy lattice sides formed by six adjoining anions and are said to be octahedrally coordinated. These spinels are known as normal spinels and are formulated as AB O Examples of normal ferrites are Zinc ferrite and cadmium ferrite. In other spinels, half the type B cations occupy tetrahedral sites, While the other half of the type B cations and the type A cations share octahedral sites. These spinels are known as inverse spinels and are formulated as BA B0 Examples of inverse ferrites are the ferrites of copper, magnesium, nickel, and cobalt. By combining a normal and an inverse ferrite, a mixed normal and inverse ferrite, such as a nickel-zinc ferrite is obtained.

The present invention stems from the unexpected discovery that the combination of the substituted ferrite end member and the normal, inverse, or mixed ferrite end member in a solid solution produces a synergistic effect, i.e., the resultant ferrite material has significantly improved properties which are not predictable from the properties of the two end members. For example, the permeability of many of the inventive ferrites is considerably higher than that of either end member alone. This is especially true of the ferrites having zinc ferrite or cadmium ferrite as an end member.

The amount of the substituted ferrite end member in the inventive ferrite compositions can range from about 20 to about 99 mole percent, and is preferably between about 30 and about 80 mole percent. It is to be understood that all mole percentages referred to herein are based on a basic composition in whose formulary description the oxygen ion contents of the two end members are matched, as indicated by the quantity (l-i-ZlF-Sc) in the aforedescribed formula. Also, in order to obtain the desired magnetic spinel structure in the Subject ferritic compositions, it is essential that the total R2 0 content be at least about mole percent of the final composition.

Briefly stated, the ferrites of the invention are prepared by finely dividing oxides or carbonates containing the desired ions, mixing the same in the dry state, wet milling a slurry of the reactants, drying the slurry, precalcining the dried slurry to a temperature below the particular final sintering temperature for these reactants to effect substantially complete transformation thereof to the ferrite form; cooling the calcined mass and repulverizing the resultant calcine; forming a compressed body therefrom, preferably with plasticizers and bonding agents; firing the formed body at a temperature of 950 C. to

1350 C. and then cooling the fired body.

In a series of examples of the invention, a number of different compositions were prepared from mixtures of appropriate amounts of the desired oxides, using Li CO as a source of Li O. For examp e a ferrite having the formula Li Ti Zn Fc 0 was prepared from 9.25 grams Li CO 5.00 grams TiO 54.00 grams ZnO, and 187.00 grams Fe O These oxides and carbonate were mixed as a slurry with alcohol for approximately one hour, and the resulting powder mixture was then placed in fire clay crucibles and calcined at 1050" C. to 1250 C. for two hours in an air atmosphere. The resulting ferrite powder, which consisted only of a spinel phase, was milled with alcohol (100 cc. for the specific mixture given above) in a porcelain mill with Alundurn balls for five hours. The slurry was then discharged and permitted to dry in an oven at 55 C. The fine-ground ferrite powder was mixed thoroughly with a 2 percent solution of methocel (30 cc. of solution to grams of ferrite powder), and the slurry was then permitted to dry at C. to a hard cake, which was pulverized to pass a 20 mesh sieve. Five percent water was added to this powder, and the mixture was sealed in a jar and allowed to stand overnight. The powder was then pressed as bars and toroids under a load of 5-000 p.s.i. The toroids were fired on setters lined with platinum at a peak temperature of 1285 C. for periods of 4 to 16 hours. The rate of heating to the peak temperature was 200 C. per hour in an air atmosphere, and cooling was at the normal free kiln cooling rate.

The end members of the general compositions produced by the aforedescribed procedure are shown in the following table:

Code Designations Composition It will be noted that the lithium-containing substituted ferrite end members listed above contain a variable total of 16 to 8 oxygen ions in the respective formulations, whereas the normal zinc ferrite end member contains only four oxygen ions. Therefore, batches were made up on the basis of matching oxygen ion content, as shown in the following tabulation:

The ferrite compositions of this invention can be prepared from starting reaction mixtures other than the approximately stoichiometric compositions. For example, compositions which fall within the two-phase and multiphase compatibility triangles as described hereinabove with reference to the drawings will always produce a ferrite composition of this invention. Where the starting composition is within the compatibility triangles and is not a stoichiometric composition, the ferrite product of this invention will be mixed with one or more additioinal materials which are not ferrites. These additional materials tend to reduce the magnetic permeability of the product. However, even when the product s a mixture of ferrite and non-ferrite, the ferrite composition of this invention will always be present as a distinct and identifiable phase.

The specific compositions produced by the aforedescribed procedure are listed in the following tables along with the properties of each composition. In Tables I-X the zinc ferrite ratio in the third column of the tables is expressed in mole percent and corresponds to the quantity (-m) in the general formula for the ferrite compositions of this invention.

TABLE I.-PROPERTIES OF SINTERED FERRITE BAR CORESCOMPOSITION SERIES [1.0 (L120-5F6z0a)-4.0(Z1IO-F8203)] Zinc Code No. Ferrite Core Apparent Theoretical Permeability Quality Resistivity Ratio, Volume, Filling Density, Density (Log Value) 2010 L2 Percent crnfi Factor gJcm. Percent Observed Computed" Observed Qu/Qo ohm-cm.

A 1 0 4. 77 0. 230 4. 16 87. 8 6. 77 31. 8 30 0. 38 4. 83 C 2 10 4. 60 0. 222 4. 17 86. 7 8. 12 40. 4 23 0. 29 4. 36 E 3 20 4. 49 0. 217 4. 22 86. 7 9. 02 44. 6 36 0. 46 2. 75 G 4 30 4. 69 0.226 4. 19 85. 0 10. 37 57. 8 23 0. 29 3. 88 I 5 40 4. 27 0. 206 4. 37 87. 5 9. 66 53. 3 34 0. 43 2. 68 K 6 50 3. 97 0. 192 4. 46 88. 1 9. 00 53. 4 31 0. 39 2. 54 M 7 60 5. 05 0.244 4. 72 92. 2 10. 98 51.0 21 0. 27 2. 58 N 8 65 3. 59 0. 173 4. 62 89. 8 9. 32 62. 7 17 0.22 2. 45 O 9 70 3. 66 0. 177 4. 69 90. 5 9. 35 61. 0 11 0. 14 2. 34 P. 10 75 3. 52 0. 170 4. 63 89. 0 2. 69 13. 7 17 0. 22 2. 32 Q 11 80 3. 72 0. 181 4. 72 90. 3 1. 39 3. 7 31 0. 39 2. 30 S 12 90 3. 0. 184 4. 75 90.0 1. 02 1. 1 74 0. 94 2. 32

V =20.7 Qo= 79 Observed efiective relative initial permeability. "Computed effective relative initial permeability at 100 percent coil occupancy: N 0rE.Frequency: 0.90 mc./s.

TABLE 1I.PROPERTIES OF SINTERED FERRITE BAR CORESCOMPOSITION SERIES [1.0 (L120-0.5T102-4F6203)-3.5 (ZnO-F82O Zinc Code No. Ferrite Core Apparent Theoretical Permeability Quality Resistivity Ratio, Volume, Filling Density, Density, (Log Value) 218 LTZ Percent crn. Factor g./cm. Percent Observed Computed Observed (Qt/Q0 ohm-cm 14 0 3. 88 0. 188 4. 19 90. 5 5.00 27. 8 51 0. 68 1. 9 9 C 15 1O 3. 73 0. 180 4. 36 92. 5 5. 77 34. 8 45 0. 60 2. 11 E 16 3. 94 0. 190 4. 37 91. 4 6. 84 39. 6 46 0. 61 2. 00 G 17 3. 90 0. 188 4. 33 89. 2 8. 43 50. 8 37 0. 49 2. 42 I. 18 40 4. l1 0. 198 4. 88. 3 10. 00 58. 6 32 0.43 2. 20 K 19 50 4. 24 0. 205 4. 34 86. 8 10. 90 61. 4 29 0. 39 3. 87 M 20 60 3. 87 O. 187 4. 50 88. 8 11. 03 70. 4 24 0. 32 3. 93 N 21 65 3. 89 0. 188 4. 51 88. 5 10.95 67. 4 22 0. 29 4. 64 O 22 70 4. 16 0. 202 4 56 88. 9 10. 78 61. 8 16 0. 21 4. 85 P. 23 75 3. 88 0. 188 4. 70 90. 8 5. 88 33. 7 12 0. 16 3. 54 Q 24 80 3. 72 0. 180 4. 74 91. 1 1. 84 7.0 18 0. 24 2. 04 S 25 90 3. 78 0. 183 4. 83 91. 5 1. 03 1. 2 67 0.89 2. 43

Observed efiective relative initial permeability. Computed effective relative initial permeability at 100 percent coil occupancy. N0rE.Frequency; 0.85 Inc./s.

TABLE lIL-PROPERTIES OF SINTERED FERRITE BAR CORES-COMPOSITION SERIES [1.0 (LigO-1.0TiO2-3Fe 03)3.0 (ZHO-FG203)] Zinc Code No. Ferrite Core Apparent Theoretical Permeability Quality Resistivity Ratio, Volume, Filling ensity, Density, (Log Value),

226 LTZ Percent 0111. Factor g./cm 3 Percent Observed* Computed Observed Qc/Qo ohm-cm Observed efiective relative initial permeability. Computed effective relative initial permeability at 0011 occupancy. No'rE.-Frequency: 0.85 mcJs.

TABLE IV.-PROPERTIES OF SINTERED FERRIIE BAR CORES-COMPOSITION SERIES [1.0 (L-1.5TiOz-2Fe2O )2.5 (ZnO-FezOQ] Zinc Code No. Ferrite Core Apparent Theoretical Permeability Quality Resistivity Ratio, Volume, Filling ensi Density, (Log Value), 234 LTZ Percent cm. Factor gJcm 3 Percent Observed* Computed Observed Qo/Qo ohm-cm A 26 0 5. 00 0. 242 3. 54 82. 9 4. 81 20. 1 53 0, 7 4. 91 O 27 10 5. 05 0.244 3. 66 83. 5 6. 98 30. 8 40 0. 51 4. 8 E 28 20 5. 21 0. 252 3. 74 83. 3 8. 85 38. 8 11 0. 14 4. 7 G 29 30 5. 08 0.245 3. 82 82. 0 10. 62 48. 9 12 0. 15 4. 7 I 30 40 5. 28 0. 255 4. 27 90. 5 12.38 55. 1 15 0. 19 4. 6 K 31 50 4. 92 0.238 4.04 83. 5 13.02 63. 1 l6 0 20 4. 6 L 32 55 4. 61 0. 223 4. 13 84. 7 13. 60 70. 6 15 0. 19 4. 5 M 33 60 4. 53 0. 218 4. 25 86. 3 13. 60 72. 6 12 0. 15 4. 2 N. 34 65 4. 38 0. 212 4. 30 86.4 12. 83 70. 2 12 0. 15 3. 3 O 35 70 4. 45 0. 215 4. 36 86. 7 3. 50 15. 6 10 0. 13 3. 4 Q 36 80 4. 34 0. 210 4. 49 87. 5 1.07 5.0 53 0. 67 2. 65 S 87 90 3. 92 0. 4. 74 90. 6 1. 02 1. 1 76 0 96 2. 71

*Observed effective relative initial permeability. Computed efiective relative initial permeability at 100% 0011 occupancy. Norm-Frequency: 0.00 mc./s.

TABLE V.PROPERTIES OF SINTERED FERRITE BAR CORES COMPOSITION SERIES [1.0 (Lig-2.0TiOz-Fe:O )2.0 (ZnO-FeiOQ] Zinc Code No. Ferrite Core Apparent Theoretical Permeability Quality Resistivity Ratio, Volume, Filling Density, Density, (Log Value), LTZ Percent cm 3 Factor g./cm. Percent 0bserved* Computed" Observed Q. Q., ohm-cm.

Vo= 20. 7 Qo=75 Observed efiective relative initial permeability.

** Computed efiective relative initial permeability at coil occupancy.-

Specimen cracked. orE.-Frequency: 0.90 mc.ls.

TABLE VI.-PROPERTIES OF SINTERED FERRITE TOROID CORES-COMPOSIIION SERIES [1.0 (LlzO-5FezO )-4.0 (ZnO'FezOM Code No. Zinc Fer- Core Apparent Theoretical Observed* rite Ratio, Volume, Density, Density, Perme- Toroidal 2010 Z Percent cm. gJcm. Percent ability Quality QQIQO lltQt HQ. llmQ.

A 1 0 3. 91 4. 18 88. 0 39. 2 2. 15 4, 508 67. 1 00022 C 2 10 3. 94 4. 14 86. 0 64. 5 108 2. 04 6, 966 83. 5 00014 E, 3 20 3. 75 4. 33 85. 4 89. 6 154 2. 91 13, 798 117. 5 00007 G 4 30 3. 88 4. 23 85. 8 134. 0 154 2. 91 20, 636 143. 7 00005 L 5 40 3. 61 4. 31 86. 5 134. 9 155 2. 92 20,910 144. 6 00005 K 6 50 3. 46 4. 36 86. 2 163. 5 137 2. 58 22, 400 149. 7 00005 M 7 60 2. 98 4. 73 92. 5 97. 3 77 1. 45 7, 492 86. 6 00013 N 8 65 2. 90 4. 57 89. 0 94. 0 58 1. 09 5, 487 74. 1 00018 O 9 70 2. 92 4. 67 90. 3 79. 6 42 0. 79 3, 343 57. 8 00030 P 10 75 3. 00 4. 70 90. 5 20.9 46 0. 87 963 31. 0 00104 Q 11 80 3. 14 4. 68 89. 5 3. 9 48 0. 91 187 13. 7 0535 S 12 90 3. 15 4. 75 90. 0 1. 3 51 0. 96 66 8. 1 0151 Qo=53 oQo=53 7. 3 0189 Observed effective absolute initial permeability. Norm-Frequency: 1.177 mcJs.

TABLE VII.PROPERTIES OF SINTERED FERRITE TOROID OORES-COMPOSITION SE RIES [1.0 (L-0.5Ti0z-4F8 O3)-3.5 (ZnO'Fe2O3)] Code N o. Zinc Fer- Core Apparent Theoretical Observed rite Ratio, Volume, Density, Density, Perme- Toroidal 218 LTZ Percent em. gJcm. Percent ability Quality Qu/Qo MQ: 1/ l tQt llmQ A 14 0 3. 22 4. 20 90. 6 32. 0 107 2. 02 3, 424 58. 5 0002 C. 15 10 3. 18 4. 29 90. 8 46. 6 118 2. 23 5, 499 74. 2 01 E 16 20 3. 17 4. 48 93. 8 71. 3 136 2. 57 9, 697 98. 5 0001 G 17 30 3. 22 4. 29 88. 3 114. 4 2. 64 16, 016 126. 6 00006 I 18 40 3. 41 4. 40 89. 3 153. 8 148 2. 79 762 150. 9 00004 K 19 50 3. 46 4. 44 89. 1 197. 5 136 2. 57 26, 860 163. 9 00004 M 20 60 3. 19 4. 51 89. 0 204. 0 97 1. 83 19, 788 140. 7 00005 N 21 65 3. 22 4. 51 B8. 7 171. 0 1. 57 14, 193 119. 1 00007 O 22 70 3. 31 4. 60 89. 6 131. 8 59 1. 11 7, 776 88. 2 00013 P 23 75 3. 34 4. 52 87. 5 40. 1 38 0. 72 1, 524 39. 0 00066 Q 24 80 3. 12 4. 59 88. 2 6. l 42 0. 79 256 16. 0 00390 S 25 00 3. 09 4. 76 90. 3 2. 2 0. 98 114 10. 7 00878 =53 uoQo=53 7. 3 0180 Observed effective absolute initial permeability. NorE.Frequoncy: 1.177 meJs.

TABLE VIIL-PROPERTIES 0F SINTERED FERRI'IE TOROID CORES-COMPOSIIION SERIES [1.0(Liz0-1.0Ti02-3Fe2O )-3.0(Zn0-1913203)] Code No. Zinc Fer- Core Apparent Theoretical Observeci* rite Ratio, Volume, Density, Density, Perme- Toroldal 226 LTZ Percent cm. g. lcm. Percent ability Quality Q IQ Q. Q. 11 1.61,

A 1 0 4. 89 3.95 88.3 42 2 76 1. 43 3,207 56.6 00031 C- 2 10 4. 40 3. 69 80. 6 46 0 54 1. 02 2, 484 49. 8 00040 E 3 20 4. 33 3. 85 82. 5 85. 4 59 1. 11 5, 089 71. 0 00020 G 4 30 4. 33 3. 86 81. 4 105. 8 82 1. 55 8, 676 93. 2 00012 I. 5 40 5. l1 3. 79 78. 5 144. 2 94 1. 13, 555 116. 4 00007 K 6 50 5. 13 3. 95 80.2 234.3 112 2 11 26, 242 162. 0 .00004 L, 7 55 4. 31 4. 25 85. 5 221. 7 97 1. 83 21, 505 146. 7 0005 M 8 60 3. 34 4. 16 83. 1 227. 2 67 1. 26 15, 222 123. 4 00007 N 9 65 3. 48 4. 18 82. 8 251. 0 56 1. 06 14, 056 118. 6 00007 O 10 70 3. 80 4. 25 83. 7 245. 2 50 0. 94 12, 260 110. 7 00008 P- 11 75 3. 31 4. 47 87. 2 24. 9 27 0. 51 672 25. 9 00148 Q 12 80 3. 20 4. 54 87. 7 2. 5 0. 96 128 11. 3 00786 S 13 90 3. 23 4. 89 92. 0 (T) Observed efiective absolute initial permeability. 1 Specimen cracked. N own-Frequency: 1.177 mole.

TABLE IX.PROPERTIES OF SINTERED FERRITE TOROID CORESCOMPOSITION SERIES [1.0(Li2O-1.5Ti02-2FezOr)2.5(ZnO-Fe O Code No. Zinc Fer- Core Apparent Theoretical Observed rite Ratio, Volume, Density, Density, Perme- Toroidal 234 Z Percent cm. g./cm. Percent ability Quality Qe/Qo l tQt \htQt ll Qt 26 4. 12 3. 36 78. 5 23. 8 80 1. 87 1, 904 43. 6 00053 27 4. 28 3. 48 79. 5 36. 0 84 1. 96 3, 024 55. 0 00033 28 4. 39 3. 61 80. 4 67. 8 36 0. 84 2, 441 49. 4 00041 29 30 4. 42 3. 64 79. 0 97. 9 48 1. 12 4, 699 68. 6 00021 30 4. 48 3. 89 82. 4 189. 0 73 1. 71 13, 797 117. 5 00007 31 4. 04 4. 02 83. 3 349. 0 85 1. 99 29, 665 172. 2 00003 32 3. 82 4. 14 85.0 450. 0 78 1. 82 100 187. 4 00003 33 3. 84 4. 18 84. 8 546. 0 68 1. 59 37, 128 192. 7 00003 34 3. 63 4. 28 86. 0 -352. 0 47 1. 10 16, 544 128. 6 00006 35 3. 09 4. 33 86. 2 16. 2 26 0. 61 421 20. 5 0024 36 3. 60 4. 47 87. 2 1. 9 42 0. 98 80 9. 0 0125 37 3. 42 4. 57 87. 5 1. 1 42 0. 98 46 6. 8 023 Qo=53 I- oQ0=43 6. 6 023 Observed efiective absolute initial permeability. N o'rE.Frequency: 1.177 me./s.

TABLE X.PROPE RIIES OF SINTE RED FERRITE TOROID CORES-COMPOSITION SERIES [1.0(L1zO-2.0T102-1 Fe20a)-2.0(ZnO-Fe O Code No. Zine Fer- Core Apparent Theoretical Observed rite Ratio, Volume, Density, Density, Perme- Toroidal 242 Z Percent 0111. g. lcm. Percent ability Quality Q.,/Q Q, 0 Q, 1/,,,

A 38 0 (i) C 39 10 (t) E 40 20 4. 48 8 35. 0 32 0.74 1, 33.5 0 00089 G 41 30 4. 56 3. 71 84. 5 64. 6 49 1. 14 3, 56. 3 00032 I 42 40 4. 88 3. 74 82. 5 124. 7 59 1. 37 7, 357 85. 8 00014 K 43 50 4. 54 3. 86 82. 5 306. 0 63 1. 46 19, 278 138. 8 00005 L 44 55 4. 64 3. 82 80. 7 508.0 63 1. 46 32, 004 178. 9 00003 M 45 60 4. 30 3. 99 83. 0 437. 0 49 1. 14 21, 413 146. 3 00005 N 46 65 4. 00 4. 17 85. 5 15. 6 26 0.60 406 20. 2 00246 O 47 70 3. 82 4. 22 85. 5 2. 9 40 0. 93 116 10. 8 0086 Q 48 80 3. 77 4. 33 85. 3 1. 6 42 0. 98 67 8. 2 0149 s 49 90 3. 70 4. 22 81. 2 1. 8 43 1. 00 77 8. 8 0130 Qo=43 #oQo=43 6. 6 0232 Observed effective absolute initial permeability.

T Specimens broken.

No'rE.Frequency: 1.177 mc./s.

As can be seen from the foregoing data, the addition of zinc ferrite to the various substituted ferrites produces complex substituted ferrite compositions with substantially improved permeabilities. As the amount of zinc ferrite in the final composition is increased, the permeability increases rapidly to a maximum and then decreases, the permeability generally dropping below that of the original substituted ferrite alone as the substituted ferritecontent drops below about 20 mole percent. Although the data shows the zinc ferrite content varying in increments of about 10 mole percent, the addition of at least about 1 mole percent of the zinc ferrite is usually sufficient to effect a substantial increase in permeability. Asshown by the data, the greatest increases in permeability are achieved in the preferred compositions containing between about 30 and about 80 mole percent of the substituted ferrite end member (m), which corresponds to a zinc ferrite content of between about 20 and about 70 mole percent (l00-m).

As shown by the above data, the circuit quality ratios of the inventive compositions exhibit two or more points at which extreme properties are evidenced. The resistivity follows a smooth curve, generally declining with increasing Zinc ferrite content, while the densities vary from about 79 to 94 percent of theoretical.

In order to illustrate the synergistic effect achieved by the present invention, comparative data showing the properties of certain substituted ferrite end members and their counter-compositions containing a proportion of zinc ferrite is shown in the following table:

TABLE XI.COMPARISON OF PROPERTIES OF Zllg-lgtsEE AND ZINC-CONTAINING SINTERED FERRITE h Computed Smterrng Theoretical Effective Quality Resistivity Temp, Density, Initial Ratio (Log Value) Composition (Rod or Bar Cores) 0. Percent Permeability Qc/Qo ohm-em,

1.00 Li O.5F ,O 1, 295 80.0 31. 3 0. 32 6. 27

0.35 Li O 5Fe1O 0.65 (ZIIO-FB2O3)4 1, 285 89. 8 62. 7 0.22 2. 45

0.60 LigO-5FezOg-O.4O LizO-TiOrIiFezO; 1, 313 76. 3 33. 8 0.47 3. 12

0.40 LigO-fiFezOg-QGO LiaO-TiOzBFezO; 1, 290 83.0 29.8 0.25 3. 97

Mean of the above (1,302) (79. 7) (31. 8) (0.36) (3. 55)

0.40 Li2O-0.5TiO2-4FezO 0.60 (Zn0-FezO )3.5 1,285 88.8 70. 4 0.32 3. 93

1.00 Ll20'TiOI'3Fe203 1, 250 85. 3 30. 9 0. 43 3. 78

0.40 Li- =O-1iOz-3FezO 0.60 (ZDO-FezOflz 1, 235 33. 2 72. 8 0. 20 4. 20

Sintering Theoretical Temp., Density, Perme- (Toroid Cores) 0. Percent ability Q IQO ,Q, Q/[HQQ II Q,

1.00 Li1O-5FezO 1, 280 35. 3 52. 0 1. 57 4, 316 65. 7 00023 0.50 LizO5F020rQ5O (ZnO-FezO3)4 1, 285 86. 2 163. 5 2. 58 22,400 149. 7 00005 0.60 Liz0-5F9zO -0.4O Li20-TiO2-3F6203 1,280 79. 5 40. 2 2. 43 5,186 72. 0 00019 0.40 LizO-5FezOa-Ofi0 Li10-TiOr3FerO 1, 280 79. 5 36. 4 2. 36 4, 550 67. 4 00022 Mean of the above (1, 280) (79.5) (38. 3) (2. 40) (4,868) (69. 7) 00020) 0.40 Li2O-0.5TiO2-4Fe2O 0.60 (ZnO-FezOabs 1, 285 89.0 204.0 1. 83 19, 788 140. 7 00005 1.00 Li1O-TiO2-sFezO 1, 285 87. 5 34. 4 1. 59 2, 890 53. 8 00035 0.35 LhO-TlO2-3FegO3-0.65 (ZnO-FerOm 1, 285 82. 8 251. 0 1.06 14, 056 118. 6 00007 Specimens of pure zinc ferrite (ZnO-Fe O sintered at I280" and having a theoretical density of 85% exhibited a permeability of 1.00 and a quality ratio of 0.995.

It is immediately evident from the above data that this invention increases the permeability of the substituted ferrite end members alone by as much as sevenfold. In most cases, this increase in permeability is accomplished by an increase in density and a decrease in the quality ratio. Also, the Q products and derived factors show a marked superiority over the properties of the substituted ferrite end members alone.

The ferrite materials of this invention are useful in a variety of electrical components. For example, the ferrites may be used as rod antenna cores; as cores for intermediate frequency and radio frequency coils, tuners, and transformers; as cores in television deflection yokes, magnetic amplifiers, and switching devices; as digital computer memory matrix elements; as magnetic recording heads; and as isolators or gyrators in microwave devices.

What is claimed is:

1. A ferrite material of spinel structure having the formula:

[m(Li O-bRO -cFe O [(100-m) R O-1 620 wherein b is from 0.5 to 2.5; c is from to 4; the sum of b and c is from 2.5 to 4.5; m is from about 20 to about 99 mole percent; R is one of the cations titanium and manganese; and (R'O-Fe O is a normal ferrite, an inverse ferrite, or a mixed normal and inverse ferrite, R being at least one of the cations zinc, cadmium, copper, magnesium, manganese, nickel and cobalt; said material containing at least about 10 mole percent Fe O and having a magnetic permeability higher than that of the end member (Li O-bRO -cFe O alone.

2. A ferrite material as defined in claim 1 wherein m is between about 30 and about mole percent.

3. A ferrite material as defined in claim 1 wherein R is titanium, b is from 0.5 to 2.0, and c is from 1.0 to 4.0.

4. A ferrite material in accordance with claim 3 having the formula 8. A ferrite material as defined in claim 1 wherein c is from 1.0 to 4.0.

9. A ferrite material as defined in claim 1 wherein R is titanium, R is zinc, b is from 0.5 to 2.0, and c is from 1.0 to 4.0.

References Cited UNITED STATES PATENTS 6/1956 Gorter 252-6261 7/1963 Sarakauskas 25262.59

T OBIAS E. LEVOW, Primary Examiner R. D. EDMONDS, Assistant Examiner US. Cl. X.R. 

